A one‐dimensional flume was designed and used for the quantitative measurement of the parameters of saltation and underwater collision for plastic balls transported over an unrippled bed by flowing water. Computer simulation reveals that saltation is maintained by the roughness of the bed. A geometric probability argument based only on the grain size distribution is used to derive the distance that a particle travels before entrapment, which turns out to be approximately proportional to the radius, as it has been previously measured. In the appendix the phenomenological stochastic transport equation is rederived from the basic assumptions.

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